It is known that the energy efficiency of a vehicle heating, ventilation, and air conditioning (HVAC) system can be improved while still maintaining occupant comfort if spot cooling is used to direct tempered air onto an occupant. A comfortable temperature for spot cooling air is, for example, 24° C. In contrast, air discharged by the system for general or volume cooling of the vehicle cabin is preferably much colder, 6° C. to 15° C. for example. However, since spot cooling makes occupant comfort is less reliant on the average temperature of the cabin, the total amount of air discharged for cooling of the volume of cabin can be reduced. That is, spot cooling can be used to maintain occupant comfort in spite of the occupant residing in a higher than normal cabin temperature, 28° C.-32° C. for example instead of a more typical cabin temperature of 24° C.
Prior attempts to provide spot cooling air and cabin volume cooling air at have used airflow delivered for spot cooling and cabin cooling at the same temperature. That is, air from across the evaporator had a relatively uniform temperature. Indeed, significant design effort is expended on the fan-scroll and diffuser design to achieve both airflow and temperature uniformity across the evaporator face. If distinct temperatures at different locations in a vehicle are desired, multiple evaporators are typically used, which undesirably increases system cost. Alternatively, reheating of relatively cold (e.g. 3-8° C.), conditioned air from the evaporator is used to provide comfortable spot cooling air at a warmer temperature (e.g. 24° C.), which undesirably reduces system energy efficiency.